Submitted to: Walnut Research Conference
Publication Type: Proceedings
Publication Acceptance Date: 1/1/2008
Publication Date: 1/1/2008
Citation: Gonzalez, E.T., Maccree, M.M., Zaid, M., Kluepfel, D.A. 2008. Assessing the Genetic Diversity of Agrobacterium Tumefaciens in CA Walnut Growing Regions and Resistance to the Biocontrol Agent, A. Rhizogenes K84. Walnut Research Conference. Interpretive Summary:
Technical Abstract: Crown gall of walnut (Juglans sp.), caused by the bacterium Agrobacterium tumefaciens, greatly impacts the CA walnut industry. To determine the genetic diversity of A. tumefaciens throughout the Central Valley of CA, we collected isolates from ten walnut growing counties. A total of 340 A. tumefaciens biovar 1 isolates were collected and tested for the presence of the Ti plasmid by PCR; 190 isolates were Ti-plasmid positive or virulent. To assess genetic diversity, BOX PCR profiles were generated for the confirmed virulent isolates. Additionally, we tested the ability of the biocontrol agent A. rhizogenes K84 to inhibit the growth of 27 virulent A. tumefaciens biovar 1 isolates from different counties. Fifteen isolates were found to be resistant to K84 from Kings, Butte, and Stanislaus counties. Further analysis of the genetic heterogeneity and K84 sensitivity of California A. tumefaciens isolates will facilitate the design of effective crown gall management strategies, including more precise application of K84 depending on A. tumefaciens genotype present.